A torque converter is a hydraulic unit that transfers torque between an engine and an automatic transmission. The torque converter comprises an impeller, a turbine, and a stator that are disposed in a steel shell that is full of working fluid at all times. The impeller is disposed at a rear portion (near the engine) of the steel shell, and it turns with a crankshaft of an engine. The turbine is disposed at a front portion of the steel shell (near the transmission), and is generally splined to a transmission input shaft. The turbine is free to rotate independently from the impeller.
The working fluid flows from the impeller toward the turbine in a radial outer portion of the torque converter. The working fluid then flows from the turbine toward the impeller by way of the stator in a radial inner portion of the torque converter.
The stator is disposed between the impeller and the turbine, and it is fixedly coupled to a stator shaft through a one-way clutch. The stator shaft is generally connected to a non-rotating member fixedly coupled to a transmission housing. The stator is generally made of synthetic resins or an aluminum alloy, and consists of an annular shell, an annular core, and a series of stator blades connecting the annular shell and the annular core. The stator blades are located circumferentially and equidistant from each other, and each stator couples the outer peripheral surface of the shell to the inner peripheral surface of the core.
The fuel economy of a vehicle provided with a torque converter is generally poor because the impeller rotates even while the engine is idling, whereby increasing engine load. Therefore, it is important to decrease the load caused by the stator while the engine idles. It is also important to increase the torque-transferring efficiency of the torque converter.
When the engine rotates, the working fluid is forced to a radial outer portion of the torque converter by the impeller toward the turbine. However, the working fluid flows from a radial inner portion of the turbine back a radial inner portion of the impeller.
To reduce the axial size and weight of the automatic transmission, flattening of the torque converter is needed. A dominant factor in flattening of the torque converter is a reduction in an axial size of the stator. However, if the axial size of the stator is reduced, the overall hydraulic performance of the torque converter may deteriorate.
Therefore, a new shape of the stator blade that is capable of reducing the axial size and maintaining the overall hydraulic performance would be highly desirable.